This application is based on Japanese Patent Applications No. Hei 11-137270 filed on May 18, 1999, No. Hei 11-209591 filed on Jul. 23, 1999 and No. 2000-69094 filed on Mar. 13, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus and a method for ultrasonically joining two members and a cooling device having ultrasonically joined members. For instance, the members to be joined are a radiator for radiating heat from an attached electrical component and a corrugated fin thinner than a radiator plate.
2. Description of Related Art
JP-A-8-83873 discloses a cooling device having a small blower located on a radiator plate on which a heat generator such as a CPU is attached. In this cooling device, a corrugated fin for improving heat radiation is thermally coupled with the radiator plate.
JA-A-9-253774 discloses a process for joining a thin corrugated fin and a plate ultrasonically.
According to the above-mentioned prior art, an ultrasonically joining apparatus has notched surfaces. The notched surfaces hold the fin and the plate securely and prevent a slide thereon. However,the notched surface makes a deformation on the plate. Such a deformation may increase resistance of heat conduction at a surface of the plate. As a result, it is likely that radiating efficiency decreases, and cooling capacity lowers.
JP-A-62-217646 discloses an ultrasonically joining method for joining thinner fins on a plate by vibrating the fins relative to the plate. However, according to experimental tests, cracks had been formed on the fins, specifically cracks had been formed near the louver mainly.
The present invention addresses these drawbacks by providing an improved apparatus and method for ultrasonically joining two members.
It is therefore an object of this invention to provide an improved apparatus and method, which don""t form deformation on a predetermined area of the member.
It is another object of this invention to improve a cooling efficiency of a cooling device.
It is a further object of this invention to provide an improved apparatus and method for ultrasonically joining a radiator plate and a fin of a cooling device.
It is a still further object of this invention to prevent deformation on an attaching surface of a radiator plate of a cooling device.
It is a still further object of this invention to prevent cracks on a fin of a cooling device.
It is a still further object of this invention to provide an improved cooling device.
According to a first aspect of the present invention, an apparatus for ultrasonically joining two members has a horn. The horn has a high friction surface for preventing a slide of the horn relative to the member. The high friction surface is not formed on a portion of the horn in correspondence with a first portion of the member. This apparatus prevents a deformation on the first portion of the member. Therefore, a flatness of the first portion is maintained even after the horn is pressed on the member and the horn vibrates ultrasonically.
According to a second aspect of the present invention, a method for ultrasonically joining two members includes a cutting step. In the cutting step, the high friction surface formed on the horn is cut into the second portion of the member to hold the member securely. Therefore, the first portion of the member is not deformed by the high friction surface.
The first portion of the member can provide close contact with a component to be cooled. The apparatus and method of the present invention can be applied to a manufacturing apparatus and method for a cooling device to improve a cooling efficiency.
According to a third aspect of the present invention, a method for ultrasonically joining two members includes pressing and vibrating step. In the step, a horn presses a first member against a second member thinner than the first member, and vibrates the first member relative to the second member.
The first member may be a radiator plate as a heat sink. The second member may be a fin of a cooling device.
Other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application.